1. Field of the Invention
The present invention relates generally to the construction and use of vascular catheters. More particularly, the invention relates to intravascular catheters and catheter systems employing both a fixed guide wire and a movable guide wire for positioning within the vascular system.
Arteriosclerosis, also known as atherosclerosis, is a common human ailment arising from the deposition of fatty-like substances, referred to as atheroma or plaque, on the walls of blood vessels. Such deposits occur both in peripheral blood vessels that feed the limbs of the body and coronary blood vessels which feed the heart. When deposits accumulate in localized regions of a blood vessel, blood flow is restricted and the person's health is at serious risk.
Numerous approaches for reducing and removing such vascular deposits have been proposed, including balloon angioplasty where a balloon-tipped catheter is used to dilate a region of atheroma, atherectomy where a blade or other cutting element is used to sever and remove the atheroma, and laser angioplasty where laser energy is used to ablate at least a portion of the atheroma. In addition to such therapeutic approaches, a variety of techniques for transluminal imaging of atheroma and other diseased regions of the blood vessel have been proposed, including endoscopic imaging techniques and ultrasonic imaging techniques.
With all such techniques, it is necessary to position a vascular catheter at a desired location within the blood vessel to be treated or imaged. Heretofore, two alternative approaches have generally been employed for such positioning. In the first approach, the vascular catheter is provided with a "fixed guide wire" secured to its distal end. The fixed guide wire is typically a coiled spring or other elongate resilient member having a preformed, curved tip. The catheter can be guided through branches within the vascular network by rotating the entire catheter, causing the tip of the guide wire to enter a desired branch as the catheter is moved forward.
In the second technique, an entirely separate "movable guide wire" is employed. The movable guide wire is itself a coiled spring or other resilient elongate member and includes a curved tip similar to that provided on the fixed guide wires described above. The vascular catheter being positioned includes a wire lumen which is sized to receive the movable guide wire. The movable guide wire is first positioned within the vascular system so that its distal end extends beyond the region of interest. The vascular catheter is then inserted over the movable guide wire using the wire lumen. Such procedures using movable guide wires are commonly referred to as "over-the-wire" insertional techniques.
Each approach for catheter insertion has advantages and disadvantages. The fixed guide wire system is advantageous in that it requires fewer steps for insertion, there is no separate guide wire present to interfere with the diagnostic and/or therapeutic procedure being performed, and the guide wire remains in place to allow for repositioning of the catheter at later stages of the procedure. The movable guide wire is advantageous in that it facilitates positioning of even large diameter catheters which would be difficult to manipulate using a fixed guide wire.
The disadvantages of each type of guide wire system are largely the opposites of the advantages. The fixed guide wire systems are difficult to manipulate and generally unsuitable for large diameter catheters, while the movable guide wire systems must generally remain in place to allow for subsequent repositioning of the catheter during the diagnostic or therapeutic procedure. The presence of the movable guide wire can interfere with the procedure and occupies limited space within the catheter which might otherwise be advantageously employed.
It would therefore be desirable to provide catheter constructions and insertional methods which can provide the benefits associated with both the fixed guide wire and movable guide wire systems, without the associated disadvantages. In particular, it would be desirable to provide catheters which can initially be positioned using a movable guide wire but which remain positionable even after withdrawal of the movable guide wire.
2. Description of the Background Art
U.S. Pat. No. 4,669,469 and European Patent Application 163 502, the disclosures of which are incorporated herein by reference, each describe atherectomy catheters comprising a distal housing having an axially translatable blade therein. The catheters are shown to have fixed guide wires or movable guide wires, but not both. U.S. Pat. No. 4,794,931, describes an ultrasonic imaging catheter, which is shown to employ a fixed guide wire for positioning. U.S. Pat. No. 4,597,755, describes a large diameter balloon catheter having a coil spring within its distal end. The coil spring is intended to prevent kinking of the catheter, not to aid in positioning the catheter. U.S. Pat. No. 4,571,240, describes a balloon catheter having a radiopaque marker at the distal end of the catheter body. The distal tip of the catheter is elongated, but is not suitable to act as a fixed guide wire. U.S. Pat. No. 4,582,181, describes a balloon catheter having an integral guide wire which extends the entire catheter length. The guide wire terminates in a helical coil which is attached to the distal end of the catheter. Movable guide wires are described in U.S. Pat. Nos. 4,724,846; 4,682,607; and 4,215,703; the disclosures of which are incorporated herein by reference. U.S. Pat. No. 4,586,923, describes a curved tip catheter with a mechanism for selectively deflecting said tip. U.S. Pat. No. 4,596,563, describes a catheter having a flexible tip formed continuously with the catheter body. U.S. Pat. No. 4,636,346, describes a guiding catheter intended to facilitate the introduction of vascular catheters. See also, U.S. Pat. Nos. 4,775,371; 4,677,436; and 4,627,436.